1. Field of the Invention
The present invention relates to a detergent composition. Particularly, the present invention relates to a powdery detergent composition comprising a nonionic surfactant as the main base, having high solubility and dispersibility which are not impaired even when used for washing in high-temperature water, and an excellent caking resistance even during storage under a highly humid condition, and optionally having excellent powder flowability, detergency and freedom from bleeding of the nonionic surfactant, which is liquid at ordinary temperatures, and also from the formation of water-insoluble substance during washing in high-temperature water.
2. Description of the Related Art
Nonionic surfactants are regarded as important detergents, since they have excellent durability in hard water, remarkable detergency and stain-dispersing power and extremely high biodegradability. However, many of the nonionic surfactants usually used for washing are liquid at ordinary temperatures. Therefore, when such a liquid nonionic surfactant is incorporated in a large amount into a powdery detergent composition, it gradually bleeds out to soak into the paper container and the flowability of the powdery detergent composition is seriously impaired; or it causes caking to harden the detergent composition into a mass with the lapse of time, thereby seriously reducing the commercial value thereof.
U.S. Pat. No. 4,136,051 (published on Jan. 23, 1979, Assignee: HENKEL & CIE GMBH) discloses a flowable detergent composition which comprises 30 to 100% by weight of a premix (containing 4% by weight or below of highly dispersible silicic acid, if necessary) prepared by finely distributing a nonionic surfactant over zeolite or a mixture of zeolite with an inorganic peroxide compound capable of forming hydrogen peroxide in water and 0 to 70% by weight of a spray-dried detergent composition. Japanese Patent publication-A No. 89300/1986 (published on May 7, 1986) discloses a granular detergent composition containing a nonionic surfactant as a detergent composition having a high flowability and an excellent caking resistance, which comprises granules prepared by mixing water-insoluble granules with silica powder, spraying a nonionic surfactant over the resultant mixture, adding zeolite powder to the resultant mixture and granulating the resultant mixture, and a granular detergent composition containing an anionic surfactant.
However, these disclosures relate to detergent additives containing nonionic surfactants to be added afterward to a spray-dried detergent containing an anionic surfactant as the main detergent base. In fact, detergents comprising a nonionic surfactant as the main detergent base as those in the present invention have not been fully investigated yet.
Great Britain Patent Publication-A No. 1474856 (published on May 25, 1977) discloses a freely flowable detergent composition which comprises a porous aggregate of a synthetic amorphous silica derivative and a nonionic surfactant.
As will be understood from these disclosures, it is known to use a silicious substance for improving the flowability of a detergent composition containing a nonionic surfactant. However, when a silicious substance is incorporated into a zeolite-containing detergent composition, the solubility of the detergent composition tends to be reduced with the elapse of time during storage under a high-humidity condition. Thus, a further improvement has been demanded.
The present inventors previously found that the above-described problem of the reduction in the solubility with the elapse of time during storage under a high-humid condition could be solved by a nonionic powdery detergent composition comprising a specific silica derivative, a nonionic surfactant and a zeolite [see European Patent Publication-A No. 477974 (published on Apr. 1, 1992)]. The present inventors also found that the above-described defects could be remarkably reduced by combining a nonionic surfactant, a zeolite, an amorphous silicious substance having specific properties and sodium carbonate in a specific proportion [see European Patent Publication-A No. 477974 (published on Apr. 1, 1992)]. However, these detergent compositions necessitated a further improvement, since their solubility and dispersibility tended to be reduced when they were used for washing with water at high temperature in summer or as is usual in the U.S.A. or European countries.